Calendars and Years II: Astronomy and Time in the Ancient and Medieval World. According to reports on the web, Aldana has shown that work by Floyd Lounsbury in the 1970s that supposedly confirmed earlier correlations of the two calendars did not in fact prove that a unique correlation between the two calendars.
This is of course important because it raises the possibility that the world will not, in fact, end in 2012, as many popular books on the "2012 phenomenon" have suggested, but perhaps many years later -- or, conversely, that the world in fact ended decades ago, and we just failed to notice. This news will perhaps come as a relief to Harold Camping, who predicted that the world would end in 1994 (Gregorian calendar), though he has since moved on to a new date, so perhaps it will not comfort him.
That the end of a period of the Mayan calendar does not, in fact, signify the end of the world is of course another possibility, arguably the only one actually backed by logic and evidence, but it's not nearly as interesting.